Process of making pressure sensitive record material



Patented Apr. 25, 1956 PROCESS OF MAKINGFPRESSURE SENSITIVE RECORD MATERIAL Barrett H. Green, Dayton, Ohio, assignor to The National Cash Register Company, Dayton, Ohio, a corporation of Maryland No Drawing. Original application November 8,

STATES PATENT OFFICE 1947, Serial No. 784,939. Divided and thisapplication December 2, 1948, SerialNo. 63,218

(Oh Lin-36) color may be produced by the mere application of localized pressure, and which is not subject to the disadvantages inherent in the pressuresensitive record material disclosed in United States Letters Patent No. 2,299,693, patented October 20, 1942, on the application filed by i Barrett K. Green on February 23, 1940. That patent discloses a pressure-sensitive record material including the combination of an insulating medium, a rupturable solid material such as gum dammar, having included therein interspersed droplets of 'a plurality of liquid reagents, which are chemically reactive to produce a distinctive color in the record material at the points of application of localized pressure thereto, such pressure rupturing the insulating medium to permit chemical reaction between the two liquid reagents. The two reagents disclosed in this patent are gallic acid and ferric ammonium sulphate, each dissolved in glycerine. These reagents are ionized by the glycerine, which constitutes an ionizing medium, and the chemical reaction proceeds by interchange of ions when the two solutions are allowed to mix, upon the rupture of the insulating medium. The reaction disclosed in that patent depends upon the presence of the reagents in an ionizing medium. However, any available ionizing medium ishy- 'groscopic, with the result that the record material, made in accordance with this patenh is sensitive to an excess of moisture, and condii tions of'high humidity may cause the insulating medium to cease to be efiective, with the resuit that the chemical reaction takes place without any application of localized pressure, and the record material is stained and discolored, so

that it ceases to be useful.

As stated above, the principal object of the present invention is to WPIOVlCIQ a process of making a pressure-sensitive record material that is not subject to the defects and disadvantages of that disclosed in PatentNo. 2,299,693, as indicated above.

Another object of the present invention is to provide a process of making a recordpmaterial upon which a mark of distinctive color may be produced-at the points-of application of localized pressure thereto, by such mere application of localized pressure, and which will not become discolored or'stained due to the effect of light,

atmospheric conditions, .or aging.

In short, itlis the object of this invention to provide aprocess of making apressure-sensitive record material in which the m'arkof distinctive color will be produced only at the points of application of localizedpressure, and at no other points, and under no other conditions.

Another object of this invention is to provide a process for making a pressure-sensitive record material in which the mark of distinctive color is produced by the chemical reaction of colorforming reactantsin theabsence of any liquid ionizing medium therefor.

A further object of this invention is to provide a process of making a pressure-sensitive record material in which a mark of distinctive color is produced by a reaction between solid particles of color-forming reactants.

Further objects, and objects relating to details and economies of operation, will defin tely appear from the detailed descriptionto follow. The objects of thisinvention have been attained by the several embodiments thereof described'in detail in the following specification. This invention is clearly defined and pointed out in the appended A claims.

In general, the present-invention contemplates a process of making a pressure-sensitive record material including the forming on a support ing member a filmqike deposit of solid particles of a plurality of adsorption color-forming reactants disposedfln contlguity with each other, such reactants being so selected that they react,

in the absence of a liquidionizing medium for the record material, as by drawing a stylus across it, the insulating medium is ruptured at the points of application of said localized pressure, and such rupture permits color-forming reaction contact between the reactants at such points, in the absence of any liquid ionizing medium for said reactants. The result is that a mark of distinctive color is produced by the mere application of localized pressure.

The color reaction employed is of the, so-called, adsorption type in which an inorganic compound causes a color change in an organic compound coming into adsorption contact therewith.

Of the reactant materials employed the organic material is an electron donor aromatic compound having a double bond system which is convertible to a more highly polarized conjugated form upon taking part in an electron acceptor-donor solid surface chemical reaction, giving it a distinctive color, and the inorganic material is a material which is an acid relative to the organic material so as to be an electron acceptor when in adsorption contact therewith. Both materials are in fine particle form in order to furnish a large reactant surface area per unit area of the record material which enhances the depth of color per unit area of the record material. 7

According to one embodiment of the invention, solid particles of one of the color-forming reactants are carried by and dispersed in a solid insun lating medium, to which a coating of solid particles of another color-forming reactant is applied. In this case, the application of localized pressure ruptures the solid insulating medium, at the points of application of such pressure, and brings about color-forming reaction contact between the solid particles of color-forming reactants at such points, thus producing themark of distinctive color. Preferably, this pressure-sensitive record material includes a base web, such as a fibrous web of paper or the like, to which the coating of solid insulating medium and the color-forming reactants is applied.

The insulating medium is a pressure-rupturable film derived from an organic film-forming hydrophilic colloid substance.

Since it is dilficult to show precisely the spatial relationship between the solid particles of colorforming reactants, the solid insulating medium, and the base web, it is preferred not to attempt to illustrate any embodiment of this invention. by drawings.

In the following examples, there will be described embodiments of this invention, by means of which the objects of the invention have been successfully attained.

The preferred embodiment includes a Web of paper having applied thereto a coating including casein as the solid insulating medium and solid particles of two color-forming reactants-kaolin and the compound 3,3 bis(4-dimethylamino 3- methyl phenyl) phthalide, having the structural formula CH: CH;

. toluene of 3,3 bisUl-dimethylamino This record material is normally white, but a blue mark is produced thereon by the application of localized pressure, which ruptures the insulating medium, casein, and permits colorforming reaction contact between the solid particles of the reactants at the points of application of such localized pressure.

The compound 3,3 bis 4-dimethylamino 3- methyl phenyl) phthalide, referred to above, is described and claimed in the United States Letters Patent of Clyde S. Adams, Patent No. 2,443,092, issued June 8, 1948, for 3,3 bis(4-dimethylamino 3-methyl phenyl) phthalide.

This record material has been made successfully, in accordance with this embodiment of the invention, by first coating a web of paper with a solution of casein having solid particles of kaolin dispersed therein, the ratio of kaolin to casein being about ten to one. The coated paper was then dried, and there was applied to the coated side of the paper a 3% by weight solution in S-methyl phenyl) phtnalide. The excess of solution was removed from the paper, and th treated paper was dried to evaporate the solvent, leaving deposit of solid particles of the compound in and upon the film of casein, in which the solid particles of kaolin are dispersed.

When these ingredients are applied to the paper as a coating thereon, such coating weighs about .0023 pound. per square foot of surface and may have a thickness of the order of from .3065 to .601 inch. The thickness of the coating varies, of course, with the treatment to which the record. material is subjected in finishing. The solid particles of kaolin in this record material may be of about the order of ten microns in diameter, although considerable variation in particle size, is possible without any ill effects. Particle size of the phthalide material is largely determined by the method of application of that ingredient. The particles of these reactants may be as large as ten microns in diameter and frequently are much smaller.

Other organic film-forming hydrophilic colloid materials such as gelatin, methyl cellulose, starch, polyvinyl alcohol, and animal glue are representative materials that may be substituted for casein as the solid insulating medium. Any of the following inorganic materials may be substituted for kaolin as one of the color-forming reactants attapulgite (Attapulgus clay), pyrophyllite, talc, bentonite, halloysite, calcium sulphate, calcium citrate, magnesium trisilicate, zinc sulphide, zirconium dioxide, calcium phosphate, barium sulphate, and calcium fiuoricle. When any of these materials are substituted for the kaolin in this combination, the resulting record material will be white or bluish white in color, and a dark blue mark will appear thereon as the result of the application of localized pressure.

A method that has had been used successfully to make the pressure-sensitive record material described above is as follows: A slurry of kaolin and water Was prepared including fifty parts by weight of kaolin to fifty parts by weight of water, and a small amount of a suitable dispersing agent, such as sodium metaphosphate, for instance, in

the proportion of 0.075% by weight Was added to facilitate the dispersion of the particles of kaolin throughout the slurry. The addition of this dic persing agent reduces the viscosity of the slurry considerably, thus facilitating its mixing and application, and also preventing the settling of were then added to the hot casein solution. which was stirred for about fifteen minutes and allowed to cool to room temperature. The kaolin slurry and the alkaline casein solution were then thor oughly mixed and blended, in the ratio of ten parts by weight of kaolin to one part of casein, and, at this stage, a small percentagefor instance, about 0.05% by weightof a solution of equal parts by weight of tributyl phosphate in alcohol, or other anti-foaming agent, was added. This mixture of the kaolin slurry and the casein solution was then applied as a coating to the paper, and the coated paper was dried, calendered or treated in any desired way to give the proper surface finish. A solution in toluene of about 3% by weight of the phthalide material was then applied to the coated side of the paper, the excess of this solution was removed in any suitable Way, as by passing under a doctor blade, and then the treated paper was dried to evaporate the toluene, and was ready for use.

The pressure-sensitive record materials disclosed herein are not claimed in this application but are disclosed and claimed in the pending application of Barrett K. Green, Serial No. 784,938, filed November 8, 1947, for Pressuresensitive record material, and in a division Serial No. 59,429, filed November 10, 1948.

It is understood that the process of making a pressure-sensitive record material described herein is susceptible of considerable variation without departing from the spirit of the invention.

What is claimed is:

1. The process of making a pressure-sensitive record material including the forming on a supporting member a film-like deposit of solid particles of a plurality of adsorption color-forming reactants disposed in contiguity with each other and a solid insulating medium, derived from an organic film-forming hydrophilic colloid substance, insulating said reactant particles from color-forming reaction with each other, at least one of said reactants being an inorganic compound and at least another of the reactants being an organic compound adsorbable therewith, and said reactants being so selected as to react, in the absence of a liquid ionizing medium for the reactants, to form a distinctive color when brought into adsorption contact with each other, one of the color-forming reactants being the compound 3,3 bis(4-dimethylamino 3-methyl phenyl) phthalide, having structure (CH 2N- N (CH3)2 and the inorganic reactant being in fine particle form providing a large adsorbent surface area and which is an acid relative to the organic reactant so as to be an electron acceptor when in adsorption contact with said organic reactant.

2. The process of making a pressure-sensitive record material including the steps of coating a supporting member with a film of solid insulating material, derived from an organic film-forming hydrophilic colloid substance, having particles of a first color-forming solid reactant dispersed therein, and depositing on said film particles of a second color-forming solid reactant, one of said reactants being an inorganic compound and the other of said reactants being an organic compound adsorbable therewith, and said reactants being so selected as to form a distinctive color when brought into adsorption contact with each other, and said solid insulating material being such as to insulate the reactants from color-form ing reaction contact with each other, the second color-forming reactant being the compound 3,3 bis(4=-dimethylamino 3-methy1phenyl) phthalide, having the structure REFERENCES CITED The following references are of record in the file of this patent:

FOREIGN PATENTS Country Date Great Britain Jan. 4, 1943 Number 

1. THE PROCESS OF MAKING A PRESSURE-SENSITIVE RECORD MATERIAL INCLUDING THE FORMING ON A SUPPORTING MEMBER A FILM-LIKE DEPOSIT OF SOLID PARTICLES OF A PLURALITY OF ADSORPTION COLOR-FORMING REACTANTS DISPOSED IN CONTIGUITY WITH EACH OTHER AND A SOLID INSULATING MEDIUM, DERIVED FROM AN ORGANIC FILM-FORMING HYDROPHILIC COLLOID SUBSTANCE, INSULATING SAID REACTANT PARTICLES FROM COLOR-FORMING REACTION WITH EACH OTHER, AT LEAST ONE OF SAID REACTANTS BEING AN INORGANIC COMPOUND SAID AT LEAST ANOTHER OF THE REACTANTS BEING AN ORGANIC COMPOUND ADSORBABLE THEREWITH, AND SAID REACTANTS BEING SO SELECTED AS TO REACT, IN THE ABSENCE OF A LIQUID IONIZING MEDIUM FOR THE REACTANTS, TO FORM A DISTINCTIVE COLOR WHEN BROUGHT INTO ADSORPTION CONTACT WITH EACH OTHER, ONE OF THE COLOR-FORMING REACTANTS BEING THE COMPOUND 3,3 BIS(4-DIMETHYLAMINO 3-METHYL PHENYL) PHTHALIDE, HAVING STRUCTURE. 